1. Field of the Invention
The present invention relates to a sheet folding device and a sheet post-processing device using such a sheet folding device. More particularly, the present invention relates to a sheet folding device that can perform, for example, processing for folding a sheet of paper double or in three and to a sheet post-processing device using such a sheet folding device.
2. Description of the Related Art
Conventionally, there is known a sheet folding device that can perform processing for folding a sheet of paper double or in three; for example, the sheet folding device is used as a post-processing device of an image forming device such as a copying machine or a printer by being combined with the image forming device. This post-processing device performs, for example, processing for folding a sheet ejected from the image forming device double in a predetermined center position and then ejects the sheet, and thus it is unnecessary to fold the sheet after an image is formed, with the result that it is possible to reduce time and labor.
For example, in Japanese Unexamined Patent Application Publication No. 2006-213473, there is disclosed a sheet post-processing device which includes a first folding roller pair for forming a first crease in a sheet member and a second folding roller pair for forming a second crease, which presses a leading edge of the sheet member in a transport direction against a first press-reception member to form a bend in the sheet member, which guides the formed bend between the nips of the first folding roller pair to form the first crease, which then presses the formed first crease against a second press-reception member to form a bend in the sheet member, which guides the formed bend between the nips of the second folding roller pair to form the second crease and in which the first press-reception member and the second press-reception member move freely in the transport direction.
However, in a method of regulating a bend in a sheet member with the shape of a transport path to control the position of the crease of the sheet member, there is a possibility that the crease is not properly formed in a predetermined position depending on the material quality and thickness of the sheet member, the state of curling or the like. When the bend in the sheet member is strictly regulated with the transport path, the capability of transporting the sheet member is reduced, and a failure in which, for example, the sheet member is jammed is disadvantageously encountered.
The present invention is made in view of such a problem in the sheet folding device; an object of the present invention is to provide a sheet folding device and a sheet post-processing device that can perform processing for reliably folding a sheet in a predetermined position regardless of the material quality, the thickness and the like of the sheet member.